Posted tagged ‘cancer’

The first large, population-based study of real-world changes in cervical cancer screening in the era of HPV vaccination has delivered some great news: the HPV vaccine not only works, but it’s working better than expected.

Researchers looked at rates of CIN, the growth of abnormal cells in the cervix detected by Pap smears, among young women in New Mexico. Even though fewer than 40% of eligible women had received all three doses of the HPV vaccine, rates of these pre-cancerous lesions dropped by over 50%. That’s a huge impact. A safe intervention has cut the incidence of a common cancer by 50%, even in a community where HPV vaccine uptake wasn’t very good. It’s great news, and it hints at even greater news: if we can get more people vaccinated, this cancer-preventer can work even better.

Why did the vaccine work better than expected? There’s a herd effect, where vaccinated individuals help protect everybody by preventing spread of the virus. Plus, the vaccine seems to offer at least some protection against related strains. And it turns out that even women who receive less than the recommended three doses get at least some helpful immunity.

The most-used HPV vaccine in the United States goes by the brand name Gardasil-9, and it protects not only women, but men, too—especially from many cancers of the mouth and throat. Since there’s nothing analogous to a Pap smear for men, it will take longer to see these kinds of cancer-beating effects in the male population, but initial studies relying on rates of infection look very promising.

The HPV vaccine is very safe, and it’s already having a big positive effect in communities. Unfortunately, some parents have been scared away from this vaccine by irresponsible and often flagrantly false internet rumors. Don’t believe the scaremongers. Protect your kids from cancer by making sure they get their HPV vaccines.

Here’s a detailed and well-referenced post from The Skeptical Raptor explaining far more about the Gardasil vaccine, and debunking many of the myths being used to scare parents.

The media is agog over a new study, one tailor made for clickbaiting. Staid, boring old Wall Street Journal proclaimed “Cellphone-cancer link found in government study.” Mother Jones called the study “Game Changing”, and NaturalNews’s headline screams “Massive government study concludes cell phone radiation causes brain cancer.” (They also say “On all of these issues, Natural News has always been right!” Google it if you want. I’m not providing a link.)

The new data is from a preliminary release of data from 2,500 rats and mice. It hasn’t been peer-reviewed yet, or scheduled for publication. We have no idea what happened to the mice involved in this study – they weren’t mentioned. Maybe they were busy.

The rats were kept in an underground bunker (which protected them from the sun, a much larger source of radiation exposure.) Special enclosures exposed the experimental rat volunteers to cell phone radiowaves starting at gestation, through the first two years of their lives. Intense radiowaves bathed their entire bodies for 10 minutes on, 10 minutes off, 18 hours a day. For two years. Extrapolating from rat lifespans, that’s equivalent to about 50 human years. Think about that exposure: 50 years, starting before birth, using cell phones mashed up against your entire body for 9 hours a day. I get it, they want to use an absolutely maximal exposure to find even a small signal of increased risk. But does that sound remotely realistic?

Compared to the control rats, male (but not female) exposed rats had small numbers of cancers in their brains and hearts – in most groups, 1 or 2 out of 90. The control rats had zero across all of the subgroups, which is itself a surprise – these were lab rats bred to develop cancers, so cancer-causing exposures could be studied. The control (unexposed) rats also had a weirdly high early death rate (remember, this group didn’t have cell phones. They were bored to death, maybe.) In all seriousness, that seems to be a big flaw. Since cancer takes time to develop, rats in a shortened-lifespan group would almost certainly have fewer cancers at autopsy. Still – zero? Were they looking hard enough?

The new study certainly raises some good questions. How could radiowaves contribute to cancer? There’s no established plausible mechanism at these levels. Why were the results only seen in male rats? What about the mice, were they similarly affected? Why did the non-exposed rats die off early, and could that explain the effect? How do these exposures compare to a typical human way of using a cell phone, holding it in your hand to text or use an app? These are good questions. Too bad journalists covering the study didn’t try to answer them.

Ironically, just a few days earlier, a much larger study (of 45,000 people) showed exactly the opposite. What, you didn’t hear about the huge Australian study that showed no increased risk of brain cancers since the introduction of cell phones 29 years ago? Perhaps the science media is more concerned about rats than Aussies. They’re certainly more eager to get your clicks than to provide accurate or useful information.

I’ve been writing a lot about CT scans lately. Why are so many being done, and which children with head trauma really need one? CTs are really kind of neat—it’s amazing that we can peer into your body to see what’s going on in there. But like every other medical intervention and treatment, there are positives and negatives, pros and cons, a ying and a yang.

I’ve mentioned some downsides to CT scanning: they cost a lot, and often reveal incidental things that though technically “abnormal”, are meaningless. But they still cause anxiety and further costs and more CT scans for follow-up! Still, the most important problem with CT scans from a public health point of view is that they involve exposing the patient to ionizing radiation, with a resulting increased lifetime risk of cancer.

CTs use x-rays to peer through your body, the same x-rays that are used to make plain x-ray pictures. But with a CT, a whole series of x-rays are taken one after another in little “slices.” Then a computer algorithm stitches those plain films together to get the familiar CT pictures of your insides. A single CT scan exposes the body to as much radiation as 200-1000 plain x-ray films—the bigger the body part, the more net radiation is needed.

And the more radiation used, the more likely there is to be mischief. Every ionizing particle has a chance to knock into your DNA, causing damage that can lead to cancer. Now, your cells already have mechanisms in place to repair this sort of damage. But it doesn’t work 100% of the time, and the more radiation, the more damage, and the higher the chance that an important DNA change will slip through the cracks.

Your body, it should be said, is bathed in radiation every day. There are radioactive elements in the earth’s crust, and there are cosmic rays pelting your scalp even as you read this. Your body can repair the damage, almost 100% of the time. But if you add a lot of excess radiation—from occupational exposures for pilots or radiologists, or from medical diagnostic studies in a CT scanner, you increase your risks.

About 2% of the total 1.7 million cancers in the US are thought to have been caused by diagnostic radiation. Another way of looking at this: one case of extra cancer is caused by every 400 to 2,000 routine chest CT scans. That’s a broad estimate, and it illustrates how difficult it is to really pin down the risk of these studies.

The problem is that estimates of cancer rates are largely based on atomic bomb survivors, who were exposed to far more radiation and have experienced a large increased cancer rate. From them, researches have extrapolated backwards—smaller radiation doses leading to smaller, but real, increased cancer rates. But we don’t really know if this is a simple linear relationship. Do smaller radiation doses increase cancer rates proportionally, or higher or lower than relatively high doses? It is very difficult to know, because we’re talking about small exposures and small increases in population risk. But when you apply that risk to millions of people, you’ve got a significant quantity of cancers potentially triggered by well-intentioned medical testing.

As a pediatrician, I’m especially concerned. My patients have more years to live than adults, so more years to potentially develop cancer; also, their smaller bodies might provide less shielding from radiation. Because their cells are growing, their DNA may be more vulnerable to the damage caused by radiation as well.

So, what can patients and parents do to limit risk?

First, reduce studies, especially CT scans. Many are being done unnecessarily. Just a few minutes discussion may help doctors and patients understand that a CT scan does not need to be done.

Reduce doses. Newer CT technology relies on lower radiation doses. Special equipment can be used on children to further limit exposures.

When practical, choose imaging studies that do not use ionizing radiation. This includes MRI scans and ultrasounds—which do not involve any increased risk of cancer. However, these studies have their own limitations and may not always be practical or realistic substitutions.

Limit studies to the area of interest. If you have a lump in your wrist, you don’t need a CT scan of your entire arm; someone being evaluated for liver inflammation doesn’t need a CT scan that goes down to their pelvis. Also, keep in mind that some areas of the body seem inherently more at-risk for radiation damage—such as the thyroid and gonads. Those areas should be shielded or avoided if possible.

CT scanning is a life-saving, crucial medical tool. When used appropriately, it’s one of the most powerful ways we have of confirming diagnoses and evaluating potentially catastrophic problems. But they do have a down side. Doctors and patients need to discuss CT scans as they would any other medical treatment, their risks and benefits, options and alternatives, and whether they’re really needed, before the tests are done.

Last time, I wrote about the reasons for the overuse of CT scans in children. They’re incorrectly perceived as necessary, the risks are far away, and no one really cares about the costs and consequences. But I don’t mean to imply that CTs are always bad. Sometimes a CT scan really is a good idea.

Pediatric head trauma can cause significant and lasting problems, and sometimes needs urgent neurosurgical intervention. How can physicians and parents tell which children are at high risk for problems, versus children at such low risk that scanning is unnecessary?

Tworecent studies have looked at this issue critically, reviewing “clinical decision rules” that help predict what children are more or less likely to have an important finding on a CT scan after trauma. Both studies tried to identify the best ways, based on only the clinical history and exam findings, to know with close to 100% accuracy which children can safely not have CT scan after head trauma. These rules aren’t designed to “rule in” serious illness—even applying these rules, most CT scans will be normal—but they hope to at least identify which children are very, very unlikely to need a CT scan as part of their evaluation.

From these studies, there are several characteristics that make it more likely that serious injury has occurred in a child, necessitating a CT scan.

The first, and probably the most important, is a persistent change in level of consciousness. A child who is running around and playing is unlikely to have had a serious injury; a child who is listless or sleepy in the doctor’s office or emergency department is very concerning.

Another consideration is the mechanism of injury. Examples of higher-risk injuries include a car crash with ejection of the passenger or a rollover, or a cyclist without a helmet being struck by a vehicle. Also, the distance of a fall is important. Though the exact numbers vary, many doctors consider a fall onto the head of more than 5 feet for a child or 3 feet for a baby or toddler to be “high risk.” Head bonks after lo risk mechanisms (such as falling backwards onto the floor or into furniture, or running into a door) are much less likely to result in a serious head injury.

Persistent vomiting or a persistent, severe headache are symptoms that can also raise concern for a more-serious injury. Now, many children get upset and vomit once; and everyone complains of a headache right after an injury. It’s persistent or severe symptoms that are concerning.

On the physical exam, certain findings should prompt increased need for a scan. These include large raised bumps (though NOT bumps on the forehead—those are common and unlikely to represent serious injury unless accompanied by other findings), or palpable depressions in the skull from fractures, or findings that suggest a fracture at the base of the skull like blood behind the ears.

Some people consider loss of consciousness at the scene of the injury to be at least a “minor” sort of red flag. A very brief loss of consciousness is unlikely to be indicative of a problem, but it may be worthwhile to observe patients with a history of even a brief period of unconsciousness to see if other issues develop.

Studies have confirmed that if none of these “red flags” are present, the chance of there being an important finding on CT scan approaches zero. But, of course, there can’t be any guarantees—there may still be a 1 in a million chance that even lacking any of these findings, there may be something on a CT. Making clinical decisions is never 100% ironclad certain.

These rules, of course, have to be individualized. Children who are younger or who have developmental challenges may not be able to tell you about symptoms; children may have complicating health issues that may increase their risk of problems or complications. Also, the exact history is sometimes unclear. So applying these rules isn’t something I’m encouraging parents to do—these are decisions to make with your doctor’s guidance. Still, I think it helps if parents know what kinds of things doctors are looking for.

Even if one or more than one of these “positive predictors” is present, the chance of an abnormal CT is still quite small—so not everyone with one of these findings needs a scan. That ought to be an individualized decision based on the judgment of the physician, the feelings of the parents, how well follow can be assured, the overall health of the child, any many other factors. But by trying to reduce at least some of these CTs when “red flags” aren’t present, many unnecessary studies can be safely skipped.

If your child has had head trauma, go to the ED immediately if there are persistent symptoms including loss of consciousness, altered consciousness, vomiting, or severe headache. Otherwise, it may be best to call your child’s physician to discuss what happened and get guidance on whether an ED eval is needed, and what to look for, and how to help your child be more comfortable. Not everyone benefits from a CT scan, and you can do your child a big favor by keeping him out of the scanner when he doesn’t need it.

As with all medical interventions and tests, CT scans have their pros and cons. You can get nifty pictures of the inside of skulls, and you can easily diagnose brain hemorrhages and skull fractures; while at the same time, you’re exposing the patient to ionizing radiation. In the long run, all of those CT scans add up. A fair estimate blames about 2% of the cancers in the United States as being caused by diagnostic radiation (mostly CT scans.) Now, maybe that’s a fair trade-off, if the CT scans are really necessary and really help diagnose and treat patients.

But it turns out that many CTs aren’t really necessary, and end up doing more harm than good.

One of the most common scenarios in pediatrics for a CT scan is as part of the evaluation of head trauma. Now, head trauma is a serious problem, and can lead to both short- and long-term disabilities, but obviously in the world of pediatrics most head bonks don’t lead to any serious problems at all. Little kids bonk their heads all the time, because they’re reckless and fall down; big kids bonk their heads on other big kids during sports. The trick is telling which head bonks are likely to lead to problems that need to be addressed immediately, and which head bonks have caused pathology that can be diagnosed and treated based on the findings of a CT scan.

So, if many CTs aren’t needed, why are so many being done? Some possible reasons:

Parents expect them, and make a fuss if they don’t happen. This is a perception among some doctors, and there is a grain of truth here, at least sometimes. Parents, even over the phone with me, sometimes immediately want a CT ordered when their child has had head trauma. Usually some calm explanations and reassurance dispels that, but some parents really seem to think a CT is necessary. Adding to this: doctors especially in hospitals have some of their pay dictated by patient satisfaction scores, and it can literally cost doctors money when there is an “unsatisfied customer.” Though it turns out that patient satisfaction is not necessarily a reliable indicator of good health or good medicine, it’s increasingly part of the way doctors are judged and paid.

They’re quick and easy. Emergency physicians are also rated on “turnover”—how quickly they can get people through the emergency department, either admitted upstairs or sent out the door. Many of the head trauma protocols suggest a period of observation as a safe and effective way to identify children at risk for serious injury. But that takes time and space and nursing resources. It’s quicker to just get the scan.

Defensive medicine. There are no guarantees; even if a child has all of the “low risk” characteristics of head trauma that should not require a CT scan, there’s probably a 1 in 10,000 risk that there really might be something wrong. Maybe it’s entirely bad luck—maybe a brain tumor that has nothing to do with trauma. But in any case, if not doing a CT scan delays a diagnosis, even a very unlikely one, doctors feel it will expose them to a risk of a lawsuit. Who needs that? Quicker to get the scan than even think about this.

The risks of cancer from a scan is way in the future. CT scans certainly do increase the lifetime risk of cancer, but only by a small percentage—and the cancer is going to happen many, many years from now. There won’t be any lawsuit, because there is never a way to prove which people with cancer got it because of exactly which medical study. That would be like figuring out which piece of candy caused a specific cavity. The risk is real, but since it’s far away and vague, it’s easy to ignore or minimize.

No one really cares about the cost. Besides a risk of cancer, are there other downsides to getting a CT scan? Yes. One is cost—excess CTs are driving up the cost of health care, and someone is paying for them. But many people feel that it isn’t them, themselves, paying. We have our insurance, we pay our copay or deductible, and who cares what the cost is? Someone ought to, everyone thinks. Just not me.

Another risk of CTs, beyond cancer and cost, is the “incidentaloma.” That’s a made-up word that refers to something unexpected found on a test that has nothing to do with the reason the test was ordered, but nonetheless makes people worry. In other words, a scan with a very low risk of finding something important and useful may still find something. About 4% of head CT scans in children are abnormal in some way. Most of those “abnormal” findings end up meaning nothing, but they still lead to anxiety and further medical workups, including, you guessed it—more CT scans.

By the way: medical people do not call these things CAT scans. They don’t involve cats. Unless, I suppose, a vet does a CT on a cat. Then that would indeed be a cat scan. Otherwise, CT is short for Computed Tomagraphy, and no “a” is necessary for abbreviation.

Coming up, a more-specific guide to CT scans: which children with head trauma really need one?

Screening tests to looking for disease early may not always be a good thing.

On one side: The Unites States Preventative Services Task Force– or USPSTF– now recommends universal screening for HIV infection among all adults aged 15-65. Their draft statement, released this week, now agrees with the CDC’s 2008 recommendation, which essentially said the same thing in 2006.

Contrast this with a study of screening mammography published in the New England Journal of Medicine a few days ago. Looking at over 30 years of data, researchers found that up to a third of tumors identified by screening mammography were likely diagnosed incorrectly. They were in fact harmless. That’s a lot of women undergoing biopsies, surgery, radiation, and chemotherapy. The authors say that their study supports the 2009 USPSTF recommendation that most women in their 40’s not undergo routine mammograms.

So why the difference?

Whether to screen or not depends on the answers to some tricky questions:

How accurate is the screen? In the case of HIV testing, it’s very accurate. Mammography? Many false positives, and some false negatives too.

What happens after a positive screen? HIV screening tests lead to a few more blood tests to confirm the diagnosis. A positive mammo leads to biopsies and surgery and maybe more.

What happens if we miss a diagnosis? HIV positive individuals spread infection. Earlier diagnosis of HIV can not only lead to effective treatment, but also to an overall reduced risk to the population. Breast cancer isn’t contagious, and it’s unclear that earlier treatment is always better—some small tumors may regress without any treatment at all.

We have a lot more to learn about the answers to these questions, and recommendations for screening should always be based on the best available science. What strategy keeps the most people healthy, does the least harm, and is the most effective way to spend health care dollars? These answers aren’t always obvious, and new studies sometimes lead to new perspectives. But it is clear that not every screening test is a good idea for everyone.

Two chemicals are being implicated as the cancer-causing contaminent: 2-methylimidazole and 4-methylimidazole (4-MI). These chemical are created during the production of caramel coloring, which apparently involves steeping sugar in ammonia and other tasty chemicals. Modern production methods don’t seem to resemble grandma stirring a pot of sugar as it browns—and I agree with the CSPI’s objection to the name “caramel coloring,” which makes the stuff sound more wholesome than it is.

But it’s not just the name that the CSPI is criticizing. Their press release directly implicates caramel color as a carcinogen:

“The ‘caramel coloring’ used in Coca-Cola, Pepsi, and other foods is contaminated with two cancer-causing chemicals and should be banned, according to a regulatory petition filed today by the Center for Science in the Public Interest.”

Their conclusions stem from research studies, such as this one by Chan and colleagues (reference #15 in the CSPI petition), which they claim shows that these chemicals cause cancer in lab animals. However, the study does not justify their conclusion; ironically, the study might show tantalizing evidence that caramel coloring protects rodents from at least on kind of cancer.

Chan’s study is typical of toxicology research. Standard lab animals (in this case, 200 rats and mice) are fed standard rodent-chow with added amounts of the chemical in question. This study followed the animals and measured daily consumption of 4-MI for 2 years. Just how much caramel coloring did they consume? There was a range of values, with some animals eating far more than others; overall consumption was designed to fall in a range of about 30-250 mg/kg day. Using the CSPI’s estimate of up to 130 micrograms of 4-MI in a 12 oz can of cola, and estimating an average teenager weighs 110 pounds, I work out that the range of exposures is similar to a teenager drinking from 11,538 – 96, 153 cans of cola a day. Every day. For two years.

I am certain that this much soda would kill a teenager, most likely by drowning. The numbers look ridiculous, so I’ll post my math at the end.

OK, let’s just say, for the sake of argument, that our hypothetical teenager really is drinking this much soda. He has a big test to study for, or something like that. What did the study show happened to the exposed rats and mice? Though in some cases, certain cancers were occurred more frequently in the more-exposed rodents (some lung cancers, for instance), in other cases the rates of cancer didn’t show a consistent dose-response relationship (thyroid lesions in female but not male mice). There was also a complex gamish of other microscopic tissue changes at a variety of inconsistent dosing levels, seen sometimes in only one kind or gender of animal. Also, 4-MI exposure seemed to protect against possibly pre-cancerous changes in breast tissue at every exposure level. The overall mortality among exposed and control animals was the same.

Basically, there was no consistent pattern of much of anything; some animals got cancer, some did not, and their tremendous exposures to 4-MI didn’t consistently correlate with health.

Don’t misunderstand me: there’s plenty wrong with drinking soda, especially in children. Loads of sugar and acid to rot teeth, and all of those unnecessary calories contribute to obesity. So I’m not saying here that soda is good for you. I agree with the CSPI that less soda consumption can improve health. What I disagree with is the breathless worry, based on barely conclusive animal studies on phenomenally large exposures, that 4-MI is a proximal cause of cancer. The science doesn’t support that, and we ought to be more truthful with people. There’s plenty enough real worry out there, and crying wolf isn’t helping anyone raise healthier kids.

The math:

The lowest range of exposure was for male rats getting 30 mg/kg/day of 4-MI. A 12 oz can of cola contains 130 micrograms = 0.13 mg of 4-MI. Divide that by an estimated teenager’s weight of 50 kg, you get an exposure of 0.0026 mg/kg/day. 30/.0026 = 11,538 – so a teenager, to reach the lowest end of 4-MI exposure in the Chan study, needs to drink 11,538 cans of cola every day for 2 years. That would be about 2060 2 liter bottles, or about 100 of those 5 ½ gallon drums, or if you were to fill up the interior of my car (total interior capacity 14.7 cubic feet), it would be drinking ten entire Honda Accord’s worth of soda every day. Isn’t math fun?

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